In remote sensing, there is a need for making gas velocity (wind) measurements of atmospheric gases by measuring the Doppler shift of individual spectral lines. Also in remote sensing, high spectral resolution is needed to measure the temperature of the gases either by looking at the width of a spectral line or by comparing the intensity of spectrally adjacent features. In studying the properties of gaseous emissions, such as astrophysical nebulosities, atmospheric reactions (aurora and airglow), laboratory gas discharges, and in performing process monitoring of reactive gases, the spectral profile of the emitted light provides various information about the source of the emissions. Because of various factors the velocities and temperatures are variable and the mapping of these variations is required. Conventionally this is accomplished by a single channel spectrophotometer or interferometer which is scanned across the field of view to map the variation of the velocity and temperature fields. This scanning is cumbersome and inefficient, usually taking a long time. During such scans the phenomena may change. It would be advantageous to image and to map the velocities and temperatures simultaneously over the entire field.
Simultaneous images in adjacent wavelength bands are also desired. It is customary to use several parallel bore-sighted imagers with a different filter in each and take data with an image detector, such as a charge coupled device (CCD), and compare the two images taken in different wavelengths. The imagers for this task are voluminous and heavy for use in platforms such as aircraft and satellites.
In many applications, it is desirable to have only one input optics and only one detector; and to separate the light after it goes through the input optics according to wavelength and produce images side by side on a single detector. A device to perform this task was described in U.S. Pat. No. 5,024,530 to Mende. The device in the Mende patent simultaneously images several wavelength bands from a single input optics provided that the wavelength bands are widely separated. It would be advantageous to have a device that images with a single imager in wavelength bands which are very close to one another. It would be advantageous to use this device to produce images in adjacent wavelength bands to detect neighboring spectral line components of molecular bands. This is an important technique in remote sensing of gas temperature.